Introduce networking delay, packet loss, or restrict bandwidth to specified destinations on a linux host.

traffic-control.sh

#!/usr/bin/env bash

# Author: Kel Graham
# Date:   2021-03-17
# Purpose: 
#   This script uses the linux traffic control `tc` command to add delay, drop packets, etc
#   which is useful when we want to test software behaviour under stress conditions, e.g.
#   such as spiking latency between Zookeeper or Kafka nodes, simulating a data centre outage
#   or restricting bandwidth between components to simulate inter-DC resource contention.

latency_ms=50
jitter=5
packet_loss_percent=1 
network_interface=etho0

# Shared Env zookeepers; these can be as broad or specific as needed
subnets='10.0.0.1/32 10.0.2.0/16 10.0.3.15/32'

ACTION="$1"
TYPE="$2"

# Default to adding latency between subnets.
if [ -z "$TYPE" ]; then
    TYPE="delay"
fi

if [ "$ACTION" == "enable" ] || [ "$ACTION" == "start" ]; then

    # Will complain if it already exists
    /usr/sbin/tc qdisc add dev ${network_interface} root handle 1: prio > /dev/null

	echo "Setting queuing discipline..."
    if [ "$TYPE" == "delay" ]; then
        /usr/sbin/tc qdisc add dev ${network_interface} parent 1:1 handle 10: sfq #> /dev/null
        /usr/sbin/tc qdisc add dev ${network_interface} parent 1:2 handle 20: sfq #> /dev/null
        /usr/sbin/tc qdisc add dev ${network_interface} parent 1:3 handle 30: netem delay ${latency_ms}ms ${jitter}ms 20.00 #> /dev/null

        for subnet in $subnets; do 
            echo "Setting up traffic control for ${subnet}..."

            /usr/sbin/tc filter add dev ${network_interface} protocol ip parent 1:0 prio 1 u32 match ip dst ${subnet} flowid 1:3 #> /dev/null
        done
    elif [ "$TYPE" == "drop" ]; then

        #echo "1..."
        #/usr/sbin/tc qdisc add dev ${network_interface} root handle 1: prio

        echo "2..."
        /usr/sbin/tc qdisc add dev ${network_interface} parent 1:1 handle 10: sfq #> /dev/null
        /usr/sbin/tc qdisc add dev ${network_interface} parent 1:2 handle 20: sfq #> /dev/null
        /usr/sbin/tc qdisc add dev ${network_interface} parent 1:3 handle 30: netem loss 100%

        echo "3..."
        for subnet in $subnets; do 
            echo "Setting up traffic control for ${subnet}..."
            /usr/sbin/tc filter add dev ${network_interface} protocol ip parent 1:0 prio 1 u32 match ip dst ${subnet} flowid 1:3 #> /dev/null
        done
    fi


elif [ "$ACTION" == "disable" ] || [ "$ACTION" == "stop" ]; then
	echo "Stopping traffic control..."
	/usr/sbin/tc qdisc del dev ${network_interface} root

elif [ -z "$ACTION" ]; then
	echo "Usage $0 start [delay | drop]"
  echo "         stop"
	exit 0

else
	echo "No clue what to do with ${ACTION} command."
	exit 1

fi